Alphabetty problem on levels where finding words of certain length

Tiggersmudge

On the levels where I need to find words of a certain length the game very often does not count words even if correctly found. E.g. I find a four letter word, I take my turn and word is accepted, but total required for 4 letter words does not go down. Or sometimes I find a long word like 7 letters and the game counts it towards my four letter word target. Is this a fault? I am on level 48 and have experienced it on all the levels of this type. 

Tinka_Silberwolf

Maybe the word contains letters with these scrubs? I think only words with only "clean" letters count towards the target.